The present work deals with the As（Ⅴ） removal from an aqueous medium by calcined refractory grade bauxite （CRB） as a function of solution pH, time, As（Ⅴ） concentration and temperature. The residual As（Ⅴ） wa...The present work deals with the As（Ⅴ） removal from an aqueous medium by calcined refractory grade bauxite （CRB） as a function of solution pH, time, As（Ⅴ） concentration and temperature. The residual As（Ⅴ） was lowered from 2 mg/L to below 0.01 mg/L in the optimum pH range 4.0-7.0 using a 5 g/L CRB within 3 h contact time. The adsorption data fits well with Langmuir isotherm and yielded Langmuir monolayer capacity of 1.78 mg As（Ⅴ）/g of CRB at pH 7.0. Presence of anions such as silicate and phosphate decreased As（Ⅴ） adsorption efficiency. An increase temperature resulted a decrease in the amount of As（Ⅴ） adsorbed by 6%. The continuous fixed bed column study showed that at the adsorbent bed depth of 30 cm and residence time of 168 min, the CRB was capable of treating 340 bed volumes of As（V） spiked water （C0 = 2 mg/L） before breakthrough （Ce = 0.01 mg/L）. This solid adsorbent, although not reusable, can be considered for design of adsorption columns as an efficiency arsenic adsorption media.展开更多
Fixed-bed operating experimental column conditions were studied to evaluate the performance of brick from Bangui Region (in Central African Republic), coated with iron oxyhydroxide (ferrihydrite) for the removal of ir...Fixed-bed operating experimental column conditions were studied to evaluate the performance of brick from Bangui Region (in Central African Republic), coated with iron oxyhydroxide (ferrihydrite) for the removal of iron(II) from aqueous solution. The prediction of theoretical breakthrough profiles using Bohart and Adams sorption model was employed to achieve characteristic parameters such as depth of exchange zone, time required for exchange zone to move vertically, moving rate for the exchange zone and adsorption capacity useful for fixed-bed column reactor was investigated under varying operating conditions. The effects of bed depth and flow rate on iron(II) adsorption were studied. Our finding revealed that the Brick from Bangui Region (in Central African Republic), coated with ferrihydrite was a very efficient media for the removal of Fe(II) ions from water. The experimental data showed that the depth and the moving rate (10.3 ± 0.6 cm) and (0.208 ± 0.006 cm/min) respectively of the exchange zone (adsorption zone) were independent of variability of the height of the adsorbent bed column, however the variations of the flow rate affect the moving rate of the exchange zone. The bed depth service time (BDST) model was used and permitted us to predict the service times of columns operated at various flow rates and bed depths and these predicted values were compared with the experimental values.展开更多
A column study was carried out to assess the influence of accompanying anions on potassium （K） leaching at potato growing sites with different soil textures （sandy loam and clay loam） in northwestern India. Potass...A column study was carried out to assess the influence of accompanying anions on potassium （K） leaching at potato growing sites with different soil textures （sandy loam and clay loam） in northwestern India. Potassium was applied in the top 15 cm layer of soil column at 30 and 60 mg K kg-1 through different sources having different accompanying anions （CI-, SO^-, NO3 and H2PO4-）. Maximum K was retained in the top 0-15 cm layer with a sharp decrease in K content occurring in 15 30 cm layer of the soil column. The trend was similar for both levels of applied K as well as frequency of leaching and soil type. The decrease of K content in soil column after four leaching events was maximum in case of Khanaura sandy loam, while only minor decrease was observed in Hundowal clay loam when K was applied at 60 mg K kg-1, indicating higher potential of clay rich soil to adsorb K. In general, the K leaching in presence of the accompanying anions followed the order of SO4^2-≤ H2PO42- 〈 NO3 = Cl-. Highest 1 mol·L^-1 CH3COONH4-extractable K was retained when K was applied along with SO4^2- and H2PO4 anions, and the least was retained when accompanying anion was Cl-. The influence of anions was more pronounced in the light textured soil and at high amounts of K application. Higher levels of K application resulted in higher losses of K, especially in sandy loam soil as observed from the leachate concentration. Among the different K sources, the maximum amount of K leaching was noticed in the soil column amended with KC1. After four leachings, the maximum amount of K leached out was 6.40 mg L-1 in Hundowal clay loam and 9.29 mg L-1 in Khanaura sandy loam at 60 mg K kg-1 of soil application through KC1. These concentrations were lower than the recommended guideline of the World Health Organisation （12.00 mg L-1）.展开更多
Brine is a solution of salt （usually sodium chloride） in water. In different contexts, brine may refer to salt solutions ranging from about 3.5% （a typical concentration of seawater, or the lower end of solutions u...Brine is a solution of salt （usually sodium chloride） in water. In different contexts, brine may refer to salt solutions ranging from about 3.5% （a typical concentration of seawater, or the lower end of solutions used for brining foods） up to about 26% （a typical saturated solution, depending on temperature）. Adsorption onto activated carbon is the most widespread technology for the removal of pollutants from water and wastewaters. In this study, continuous fixed-bed-column systems were investigated. The adsorbents which authors use are： spruce （Picea abies） untreated, spruce modified by autohydrolysis. The column systems were filed with biomass at various initial dye concentrations, flow rates and bed-depths. The column kinetics of MB （Methylene Blue） adsorption on spruce （Picea abies） untreated, spruce modified by autohydrolysis was simulated. Economies arise when the facility that can use such adsorption materials is near a source of a lignocellulosic waste as agricultural residues, thus saving transportation cost and contributing to industrial ecology at local level.展开更多
The applications of adsorption are very important.The following is a list of some of the most common:using the adsorption effect we can achieve a high vacuum in cases of low temperature at which the adsorption of gase...The applications of adsorption are very important.The following is a list of some of the most common:using the adsorption effect we can achieve a high vacuum in cases of low temperature at which the adsorption of gases from solids is intense.Regarding,the gap we can achieve is in the range of 10-7 mmHg.Another very important application of adsorption is the separation of a mixture of gases from a certain adsorbent,which has a separate adsorption capacity for each gas.In this way it is possible to separate the noble gases,as well as gasoline and hexanes from oil.The experimental diagrams confirm the validity of the Freundlich equation for dilute solutions with low concentrations.At the same time,from the aggregate diagrams of the dilute solutions,listed above,we observe:for graph 1 concerning the adsorbent materials we used we observe that the capacity KF has a higher value for the ground cork while the lower one for olive ash.Also,for graph 2 regarding the adsorbent materials we used we observe the n of the isothermal Freundlich has a maximum for olive ash while a minimum has for two materials lentil straw and ground cork.展开更多
文摘The present work deals with the As（Ⅴ） removal from an aqueous medium by calcined refractory grade bauxite （CRB） as a function of solution pH, time, As（Ⅴ） concentration and temperature. The residual As（Ⅴ） was lowered from 2 mg/L to below 0.01 mg/L in the optimum pH range 4.0-7.0 using a 5 g/L CRB within 3 h contact time. The adsorption data fits well with Langmuir isotherm and yielded Langmuir monolayer capacity of 1.78 mg As（Ⅴ）/g of CRB at pH 7.0. Presence of anions such as silicate and phosphate decreased As（Ⅴ） adsorption efficiency. An increase temperature resulted a decrease in the amount of As（Ⅴ） adsorbed by 6%. The continuous fixed bed column study showed that at the adsorbent bed depth of 30 cm and residence time of 168 min, the CRB was capable of treating 340 bed volumes of As（V） spiked water （C0 = 2 mg/L） before breakthrough （Ce = 0.01 mg/L）. This solid adsorbent, although not reusable, can be considered for design of adsorption columns as an efficiency arsenic adsorption media.
文摘Fixed-bed operating experimental column conditions were studied to evaluate the performance of brick from Bangui Region (in Central African Republic), coated with iron oxyhydroxide (ferrihydrite) for the removal of iron(II) from aqueous solution. The prediction of theoretical breakthrough profiles using Bohart and Adams sorption model was employed to achieve characteristic parameters such as depth of exchange zone, time required for exchange zone to move vertically, moving rate for the exchange zone and adsorption capacity useful for fixed-bed column reactor was investigated under varying operating conditions. The effects of bed depth and flow rate on iron(II) adsorption were studied. Our finding revealed that the Brick from Bangui Region (in Central African Republic), coated with ferrihydrite was a very efficient media for the removal of Fe(II) ions from water. The experimental data showed that the depth and the moving rate (10.3 ± 0.6 cm) and (0.208 ± 0.006 cm/min) respectively of the exchange zone (adsorption zone) were independent of variability of the height of the adsorbent bed column, however the variations of the flow rate affect the moving rate of the exchange zone. The bed depth service time (BDST) model was used and permitted us to predict the service times of columns operated at various flow rates and bed depths and these predicted values were compared with the experimental values.
基金Supported by the Ph.D. Programme of Punjab Agricultural University (PAU), Inida
文摘A column study was carried out to assess the influence of accompanying anions on potassium （K） leaching at potato growing sites with different soil textures （sandy loam and clay loam） in northwestern India. Potassium was applied in the top 15 cm layer of soil column at 30 and 60 mg K kg-1 through different sources having different accompanying anions （CI-, SO^-, NO3 and H2PO4-）. Maximum K was retained in the top 0-15 cm layer with a sharp decrease in K content occurring in 15 30 cm layer of the soil column. The trend was similar for both levels of applied K as well as frequency of leaching and soil type. The decrease of K content in soil column after four leaching events was maximum in case of Khanaura sandy loam, while only minor decrease was observed in Hundowal clay loam when K was applied at 60 mg K kg-1, indicating higher potential of clay rich soil to adsorb K. In general, the K leaching in presence of the accompanying anions followed the order of SO4^2-≤ H2PO42- 〈 NO3 = Cl-. Highest 1 mol·L^-1 CH3COONH4-extractable K was retained when K was applied along with SO4^2- and H2PO4 anions, and the least was retained when accompanying anion was Cl-. The influence of anions was more pronounced in the light textured soil and at high amounts of K application. Higher levels of K application resulted in higher losses of K, especially in sandy loam soil as observed from the leachate concentration. Among the different K sources, the maximum amount of K leaching was noticed in the soil column amended with KC1. After four leachings, the maximum amount of K leached out was 6.40 mg L-1 in Hundowal clay loam and 9.29 mg L-1 in Khanaura sandy loam at 60 mg K kg-1 of soil application through KC1. These concentrations were lower than the recommended guideline of the World Health Organisation （12.00 mg L-1）.
文摘Brine is a solution of salt （usually sodium chloride） in water. In different contexts, brine may refer to salt solutions ranging from about 3.5% （a typical concentration of seawater, or the lower end of solutions used for brining foods） up to about 26% （a typical saturated solution, depending on temperature）. Adsorption onto activated carbon is the most widespread technology for the removal of pollutants from water and wastewaters. In this study, continuous fixed-bed-column systems were investigated. The adsorbents which authors use are： spruce （Picea abies） untreated, spruce modified by autohydrolysis. The column systems were filed with biomass at various initial dye concentrations, flow rates and bed-depths. The column kinetics of MB （Methylene Blue） adsorption on spruce （Picea abies） untreated, spruce modified by autohydrolysis was simulated. Economies arise when the facility that can use such adsorption materials is near a source of a lignocellulosic waste as agricultural residues, thus saving transportation cost and contributing to industrial ecology at local level.
文摘The applications of adsorption are very important.The following is a list of some of the most common:using the adsorption effect we can achieve a high vacuum in cases of low temperature at which the adsorption of gases from solids is intense.Regarding,the gap we can achieve is in the range of 10-7 mmHg.Another very important application of adsorption is the separation of a mixture of gases from a certain adsorbent,which has a separate adsorption capacity for each gas.In this way it is possible to separate the noble gases,as well as gasoline and hexanes from oil.The experimental diagrams confirm the validity of the Freundlich equation for dilute solutions with low concentrations.At the same time,from the aggregate diagrams of the dilute solutions,listed above,we observe:for graph 1 concerning the adsorbent materials we used we observe that the capacity KF has a higher value for the ground cork while the lower one for olive ash.Also,for graph 2 regarding the adsorbent materials we used we observe the n of the isothermal Freundlich has a maximum for olive ash while a minimum has for two materials lentil straw and ground cork.
